Flexible welding rod having organically bound core and protective sheath

ABSTRACT

Primarily intended for arc welding, the cord consists of a core formed of a mineral powder which is mixed with an organic binder and contains at least the constituents of a welding flux, the core being encased in a flexible protective sheath of organic material.

United States Patent 2468371 4/1949 i etal. "219/137 Clement et al. v 1451 Oct .3l, 1972 [54] FLEXIBLE WELDING ROD HAVING 3,493,713 2/1970 Johnson ..2l9/73 Q QRGANICALLY BOUND CORE AND 7 3,102,827 I 9/1963 Kriewall et al ..l17/ 207 PROTECTIVE'SHEATH 1 j 2,700,091 1/1955 9 Culbertson 131, ..2l9/l46 v 4 Y 1,944,753 1 1934 Mathias ..-....219 146 [72] I k 26 3,084,074 4/1963 Wasserman etal ..117/207 F 2,552,176 5/1951 l-lummitzsch ..1 17/204 Chem 1,871,257 8/1932 Cadwellm, ..'...117/202 vgnesi me 3,108,020 10/1963 Var Der Willigen =1 cygne' 91 vauhauan' al 117/207 [22] Filed:. Aug. 24, 1970 3,004,872 10/1961 Stark ..1 17/202 2,870,047 l/1959 Kce ..l'17/202 [21] 1,972,063 8/1934 Judy 17/202 I 1 .2 .2121..... ,.i;.2 :i 2;. m. 1 MW [30-], Apnhcatmn 28 Primary Examiner-J. V. Truhe A 28, 6 ,22 .8 Assistant Examiner-George A. Montanye Attorney-Cameron, Kerkam & Sutton [52] US. Cl. ..Zl9/146, 219/137 1.. 1, 1 v i [51] Int. Cl. ..B23|( 35/22 [58] Field of Search ..219/146; l17/202, 203, 204, I ABSTRACT 7/205, 207; 148/249 219/73 4 f Priinarily intended for arc welding, the cord consists 761.137 of a core formed of a mineral powder which is mixed I with an organic binder and contains at least the, con- [56] Retermces I stituents of a welding flux, the core being encased in a UNITED STATES. PATENTS a fl ible protective sheath of organic material. 2,468,372 4/1949 Landis .;219 /137 7 Claims, 3 Drawing Figures 3,345,495 10/1967 01121886181 ......'.'..2l9/146 I V Q FLEXIBLE-Wanamaker) nxvmo ORGANICALLYaoUNncom: ANn-Paomc'nva Thisinvention relates :to a cord which is primarily in tended foruse in arc welding techniques and is also concerned with a method .of arc welding .for-the practical a pplication ofacord of-this type.

One method-of ar'c welding .consistsin producing an are between the part tobewelded and a fusible electrode formed of metal or metal alloy which is intended to form the welded joint..lf a metal wire having suffi- However, a solution of this kind cannot always be-carried into practice in a conventional welding process by.

reasonof the diff culties encountered in'obtainingfusible wire of a grade which is suited on the one hand to the metal to be welded and on the other hand to the quality of the jointsto be formed.

in order to obtain a weld of good quality 'it is necessary'in the majority of cases to bring a flux of suitable composition into the arc zone at the same time as the metal wire, the intended function'of said flux being either to clean and deoxidize the part prior to welding or to form a slag which serves firstto protect the pool of molten weld metal andthen toprotect the weld during solidification. In some cases it is also-necessary to add an alloying element which is intended to combine withthe allo'y of'the metal wire'in orderto adjust the composition of the weld. A first solution consists in mineral powder also c'ontainsthe constituents of a weld 1 metal, the binder and the sheath being preferably combustible at the melting temperature of the weld metal.

supplying the flux in the formofa simple p'owderindependently of the electrode but this gives rise to the disadvantages which are inherent in the use of powders,

especially in regard to the irregular distribution ofconhinders the formation of welds. Moreover, in the first of the two alternativesjust mentioned, it is difficult to ensure a constant proportion between the weight of the flux and the weight of the metal tube at the time of manufacture; in the second alternative, the presence of the coating makes the electrode very delicate both during storage and use and hinders the supply of electric current. Furthermore, in the case' of all the'solutions mentioned, it is clearly presupposed that the essential constituent of the weld metal is a drawable alloy.

Finally, although consideration has already been given to the possibility of protecting the welding flux by means of a sheath in order to permit underwater welding, the designs proposed up to the present time always uniform composition,whichis easyto manufacture and touse, which is not delicate and has storage stability.

To this end, the invention proposes a cord for use especially in arc welding and characterized in thatit comprises a core which is formed of a mineral powder together with an organic binder and in which said powder contains atleast the'constituents of a welding flux, a flexible protective sheath of organic material being placed around said 'co're. Saidbinder and said chosen so as to "bei-totallyicombustisheath are usually ble at the temperature of utilization of thetlux. I 1 in accordance withasecondary feature,'at*least one alloying element of a weld metal 'can'be incorporated in powdered form in said core.

' -In a'preferredembodiment of the invention,- said It is often useful in this case to-form the core of the welding cord in two coaxial zones containing a powder which is bound by the organic binderand formed respectively by the constituents of the weld metal in one zone and bythe constituents of the welding flux in the otherzone.

In the cord according to the invention, the proporensured by the protective sheath; 7

The welding cord under consideration is easy to manufacture and is preferably formed by coextrusion.

In the application of the'cord in accordance withthe invention to arc welding techniques,'a fusible electrode" which is'separate from the welding flux may be employed if necessary'while the flux'is provided in the form of a cord as hereinabove defined. Accordingly, it

'ty-of electrodes which are constructed in this manner consisted of electrodes in the form of rigid rods made up of a central metal wire or an outer metal tube.

The main object of the invention is to overcome the different disadvantages.ofconventional arc welding techniques as recalled in the foregoing, especially by making it possible to ensure that welding torches are.

- flux is-composed of 'a' number of mineral elements or supplied continuously with a product which has a is an advantage to spray the flux in the hot state onto the weld zone by means of a spray torch which ensures combustion of theorganic products,-melting oftheflux I constituents and preheating of the parts to be welded while projecting the molten flux particlesonto said Parts. Y t

Further properties of the invention willbecome ap-- parent from the following description in connection withparticularmodes'of application which have been chosen by way of example. it will naturally be understood that this description is not to be interpreted in i any limiting sense so far as the scope of the invention is A few embodiments of the cord which is intended to f be utilized in the arc welding process will first be described but withoutv reference to the method of manufacture and the exact nature of the constituents.

In the embodiment of FIG. 1, the cord contains only 1 the flux constituents, which, at the time of welding, serve to form the slag for protecting the pool of molten weld metal and then the weld during solidification. The

compounds. These mineral constituents which are parweight, for example, form the core 1 of the welding cord. Said cord is covered with an outer'sheath 2 formed of a flexible. film of organic material having a thickness between 0.1 and 0.5 mm.

"At the time of a welding operation, the extremity of the cord is moved from point to point within the zone of an electric are which is formed between the parts to be welded and a fusibleelectr'ode constituted by the metal or the alloy which is intended to form the weld; I In an alternative mode of utilization which isparticul arly advantageous, the combustion of organic substances and melting of theflux are no longer produced by the arc itself, but by a spray torch which is placed next to the weldingtorch. Thespray torch accordingly projects the'molten particles of flux onto the surface of the parts to be welded and thus has a contributory function in heating the parts at the level of the weldto be formed.

In a different mode of procedure, a powdered filler metal or even a powder containing all the constituents of the weld. metal isadmixed with the constituents of the welding flux. This powder can be made up either of the actual alloy which is employed for the weld or of a metal or more simple alloy and of other separate ,constituents which will combine with each other during the welding operation.

By wayof alternative and as is illustrated in FIG. 2 coextrusion can be carried out by forming the core of the welding cord in two, coaxial zones; the metal powder which is agglomerated by an organic binder forms the centralfcylindrical portion 3 and is surrounded coaxially by the flux 4 which is agglomerated in the same manner. The s heath'2 of organic material surrounds the complete assembly.

In some applications the welding'cord can be-melted in the weld zone either with a refractory (non-consumablelelectrode' or with a-fusible (consumable) electrode. In the-first case, the cord contains together with the flux allthe constituents of the weld metal. In

position of theweld as afunction of the nature of the material to be welded and of the properties which are sought.

In another embodiment which is illustrated in FIG. 3, thewelding cord in accordance with the invention additionally comprises a metal wire 5 which is wound around the cord outside the sheath of organic material.- This arrangement makes it possible to endow the cord with surface conductivity and consequently to facilitate its use as an electrode, the properties of flexibility of said cord being nevertheless retained whilst cohesion and protection of the powder areensured by the binder and the sheath of organic material.

Whatever form of construction may be adopted among the different alternatives described in the foregoing, the cord can be fabricated in particular so as to form by coextrusion both the internal core of binder and of mineral powder (which may be coextruded in two parts if necessary) and the sheath of organic material. In the particular case in which a thermoplastic product is employed both for the binder of the core and for the sheath, the hot extrusion process is 4 preferably adopted. Otherwise, the operationv is preferably carried out in the cold state, in whichcase the products are placed either in emulsion or in solution in a suitable. diluent which is then eliminated by drying. The use of a non-aqueous organic diluent makes it possible to prevent embrittlement of the weld which could otherwise be caused by the hydrogen which is evolved at the time of dissociation of the water in an electric arc. The addition of a plasticizer serves to improve the flexibility of theproduct which is finally obtained. v 'w The same organic binder 'is' advantageously employed on the one hand for the core which contains the mineral powder and on the othershand for the outer sheath of organic materialbut organic binders of different types can also beiempioyed ln general, the

sheath .or organic material-represents aproportion of approximately 10 percent'by weight. of all the constituents of the core and of the sheath; infthe end product, this results in a sheath thickness of the order of 0.10 to 0.15 mm which is sufficient to ensure both protection and flexibility. The mineral constituents of the core are incorporated with the organicbinder in the form of a powder which preferably has a particle diameter of less than 0.5 mm. The proportion of organic binder in the core is usually within the range of 0.5 to 8 percent by weight but a higher proportion of up to30 percent by weight in particular is advantageously employed in the case of a cellulose flux in order to derive advantage from the evolution of CO 2 at the time of welding. The same effect can in any case be obtained by increasing the thickness of the sheath. j The composition of thewelding cord in accordance with the invention is specified hereinafter in a few particular examplesof application. I

' EXAMPLE 1 parts by Calcium carbonate 40 .Fluorspar 2S Cryolite v 4 Titanium dioxide l0 Ferromanganese 5 Ferrosilicon 10 This powder is screened to a particle size of less than 150 microns and there are then mixed therewith 200 parts by weight of steelpowder which is low in carbon and has a mean particle size of microns.

In respect of 100 parts of the mixture, there are then added 5 parts of polyvinyl acetate in solution in 20 parts'of ethyl acetate. After addition of 0.5 pan of plasticizer (dibutyl phthalate), the aggregate is mixed I for a period of one hour in order to ensure homogeniza tion.

The paste obtained is shaped by extrusion at the same time as another paste which is prepared in the 1 same manner but without mineral powder and which is intended to form the sheath.

At the discharge end of the extrusion press, the

productobtainedsis subjected to drying at'room tein perature for period of 24 hours in order to remove he solvent.

EXAMPLE 2 In order to weld molybdenum stainless steel having the following composition:

weight carbon 0.03 chromium l8 nickel 12 molybdenum Z 2 8 iron the remainder there was prepared a welding cord in accordance with FIG. 2 containing on the one hand the weld alloy'which is identical with the stainless steel alloy to be welded andon the other hand a flux having the following composition:

After mixing with the binder in two different pastes, namely on the one hand the alloy powder and on the other hand the flux powder, the cord is-shaped by coextrusion; the weld alloy constitutes the central zone having a diameter of approximately 4 mm and the flux forms a surrounding ring having an external diameter of 6.7 mm. The proportion of binder is'of the order of 5 percent by weight of ethylcellulose after evaporation of the ethanol which is employed as diluent. I

The sheath of organic material is formed from a paste of ethylcellulose in ethanol, there being added to the mixture 5 percent by weight of dibutyl phthalate. The proportion of said paste with respect to that which forms the core is of the order of percent by weight in order to produce a sheath having a thickness of 0.15 mm, for example, in respect of a diameter of 7 mm.

EXAMPLE 3 EXAMPLE 4 In order to weld ordinary low-carbon structural steel,

the core of the welding cord is formed from the following constituents:

parts by'weight Thermoplastic binder 2s (ethylcellulose) l6 7 Rutile The mineral constituents in the form of a powder havin ga particle size which is le'ssthan 125 microns are mixed with the powdered thermoplastic binder. The aggregate is shaped by hot extrusion. The sheath is formed by coextrusion from the same binder.

. In all the examples hereinabove described, the method according to the invention makes it possible to obtain a cord having a sufficient degree of flexibility to permit of its being wound on a spool and consequently to permit'of continuous feed to a welding =unit. Said cord has the same advantages as metal wires from the point of view of insensitivity to mechanical impactsand thermal shocks. In addition, said cord is perfectly calibrated. But on the other hand, compositions which .moisture and in delivery as is the case with free powders since it is displaced mechanically. Since it is neither delicate nor fragile, the cord can therefore be easily stored and handled.

Compared with conventionalcoated electrodes, the

welding cord makesit possible to reduce the hazards of formationof blow-holes at the time of welding by virtue of its insensitivity to moisture. The weld metal deposited is low in hydrogen and is therefore free from the embrittling action which would be due to hydrogen.-.

Melting of the electrodeis a smoother process; projections are. reduced both in number and in volume. Finally, the mechanical properties of the welded joints are improved. I What is claimed is: i i

1. In an arc welding cord the combination of a core consisting of a homogeneous agglomerated mixture of a mineral powder containing the constituents of a welding flux and an organic binder and a flexible sheath of organic material around said core.

2. A cord according'to claim 1, wherein the welding flux contains alloying elements.

3. In an arc welding cord the combination of a core consisting of a homogeneous agglomerated mixture of a mineral powder of a welding alloy and an organic binder and a flexible protective sheath of organic material around said core.

4. A cord according to claim 3, wherein said powder contains a number of separate constituents forming an alloy melting bath.

5. In an arc welding cord the combination of a core of a homogeneous mixture of a mineral powder and organic binder in each of two coaxial zones, the mineral powder being the constituents of a welding flux for one of the zones and being a welding alloy for the other zone and a flexibleprotective sheath of organic material around said core.

6. In an arc welding cord the combination of a core of a homogeneous agglomerated mixture of a mineral powder and organic binder ineach of two coaxial zones the mineral powder being the constituents of a welding flux for one zone and having separate constituents forming an alloy during-the .welding process for the other zone and a flexible protective sheath of organic material around said core.

7. A method of arc welding including the step of 'STATESPATENT OFFICE v CERTIFICATE OF CORRECTION j October 31 1972 v lr wen to rcs Re ne] Cleme nt; Pierre Man fredi and "Roger Roullia y 11:13 crtified that error appars-iri the abqvvid entifid patent and that; said Letters Patent are hrebycprredted as shown below v 73] "A 's signee; Cbmmi'ssariat A L'Energ ie Atomique and.

' Societe' De Fabriati on D'Elements Catalytiques (SPEC),

' Par is Framze and'Bollene, France.

' .Sighed. and, sealed this 17th day of"Ap-r'il l 973 (SEAL)- Attest:

EDWARD M. FLETCHER,J R.I- ROBERT GOTTSCHALK Attesting Officer I Commissioner of Pafcents T 3 a UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3 I 701-1444 Dated October 3].,

Inventor(s) Rene Clement; Pierre Manfredi and Roger Roulliay It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below 4 I x I- [73] Assignee: Commissariat A L'Energle Atomlque and 1 Societe De Fabrication D'Elements Catalytiques (SFEC) Paris, France and Bollene, France.

Signed and sealed this 17th day of April 1973 (SEAL) Attest:

EDWARD M.FLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents 

2. A cord according to claim 1, wherein the welding flux contains alloying elements.
 3. In an arc welding cord the combination of a core consisting of a homogeneous agglomerated mixture of a mineral powder of a welding alloy and an organic binder and a flexible protective sheath of organic material around said core.
 4. A cord according to claim 3, wherein said powder contains a number of separate constituents forming an alloy melting bath.
 5. In an arc welding cord the combination of a core of a homogeneous mixture of a mineral powder and organic binder in each of two coaxial zones, the mineral powder being the constituents of a welding flux for one of the zones and being a welding alloy for the other zone and a flexible protective sheath of organic material around said core.
 6. In an arc welding cord the combinatioN of a core of a homogeneous agglomerated mixture of a mineral powder and organic binder in each of two coaxial zones the mineral powder being the constituents of a welding flux for one zone and having separate constituents forming an alloy during the welding process for the other zone and a flexible protective sheath of organic material around said core.
 7. A method of arc welding including the step of melting a cord consisting of a mineral powder containing in a homogeneous agglomerated mixture the constituents of a welding flux and an organic binder and a flexible sheath of an organic material around said core in the arc zone by a spray torch. 